I want to be able to state the disadvantages of uncontrolled anthropogenic CO2 production.

Im not here to debate whether or not it is happening.

There are a LOT of sources saying this will happen, that will happen, this wont happen etc. but I have a hard time judging which ones are reliable sources.

What are the major, most substantiated consequences of continued increase in atmospheric greenhouse gases? Just the bullet points, I dont need to be given full scientific analyses.

Pretend I am scientifically competent, open minded and dont know anything about what might change about the climate - why should I stop burning coal?

***One camp says many species will become extinct due to rapid changes in the environment and habitats.Another camp says "SO what? Extinctions occur all the time."One camp says environmental changes will wreak havoc on global food production.Another camp says increased atmospheric CO2 will *increase* global food production.One camp says global population redistribution due to changes in climate will cause havoc.Another camp says more of the planet will become habitable if the temperature rises.One camp says the weather will become generally more unpredictable and severe.Another camp says "So what? We have bad weather now, it wont get so bad."etc.

***So whilst I am firmly in the camp of "Even if the outcomes are not certain, it sure does seem like a good idea to limit the production of toxic gases, especially when they mess with the weather, which is eminently unpredictable and powerful. Probably shouldnt mess with it." Im still not sure what the most powerful points are when discussing whether or not we should care about anthropogenic climate change.

I know we should, but I'd like some points to have in my pocket that cant just be countered with the simple opposite or with "So what?".

Is it a case of we "should" reduce anthopogenic CO2 production, (to save the cuddly animals and preserve our precious status quo) or we "must"? (In order to preserve life, our species, our way-of-life and the maintainability of the habitat for our descendants)

p1t1o wrote:One camp says the weather will become generally more unpredictable and severe.Another camp says "So what? We have bad weather now, it wont get so bad."

"it wont get so bad." is denial, not an argument.More storms/floods/hurricanes/droughts mean more dead people.

Also, a lot of people don't realize just how far weather prediction has come in the past few decades, and how reliant we are on that, from knowing what clothes to pack for a trip to more consequential things like crop maintenance or hurricane response.

Another biggie is that sea levels *will* rise and there *are* people living in areas that will be affected and they aren't just people living on tiny little atolls way out in the Pacific.

There's a certain amount of freedom involved in cycling: you're self-propelled and decide exactly where to go. If you see something that catches your eye to the left, you can veer off there, which isn't so easy in a car, and you can't cover as much ground walking.

Yeah, we forget so quickly that before weather satellites, we could predict weather, like, a day in advance. None of this 10-day advance forecast bullshit you get now.

And yeah, uh, most big cities in the world are port cities, and most of them have a big chunk of their land only slightly above sea level. Sea level rise = mass migration as cities become unlivable, changing weather patterns = mass starvation as food belts are destroyed (and it takes a lot of time to set up new ones as they develop in previously cold or dry areas). Climate change is gonna be the death of billions, no hyperbole.

Changes in food production will cause severe economic problems and there is a significant risk of mass starvations - efforts to solve this will take years and will not prevent initial severe consequences.Changes in habitat will force mass migrations, with accompanying severe economic and health/survival problems.Changes in weather are going to be more severe than anyone really gives credit for and will exacerbate/trigger the first two points.And basically all of these points are vastly underestimated by everyone (but mostly by the deniers).

Xanthir wrote:Climate change is gonna be the death of billions, no hyperbole.

No offence, but thats a big shout, can anyone second that? Dry realism is what Im after.

Their is reason to believe in a 2 meter sea rise with good certainty in a 100 or so years. Which would inundate a substantial portion of the current coastal areas. This will be acerbated by an accompanying increases in population, from our current levels of about 7 billion to 10 billion by 2050. Major coastal cities are moving now to adapt since they are seeing the early effects.

Water stress is high now in many places and getting worse. A lot of major population areas are running short on water. California is investigating desalinization and operating at least one plant. They are used in the Middle East and Australia. The grain belt relies on well water in a lot of cases and aquifers are getting depleted forcing farmers to drive wells deeper and deeper.

Extreme weather events seem to be becoming more common. Heat waves, droughts, tornado's and so on. But a lot of that is currently buried in statistical noise. How much of it involves normal variability and how much of it is related to climate change is open to dispute. But by the time there is a degree of certainty if we haven't started adapting it could get very ugly.

And there is no indication that if populations start to move, assuming if things get as bad as predicted, that they will be welcomed. They don't seem to be now and it is hard to see that getting better over time. That raises the risk of war. Certainly the Pentagon takes that risk seriously.

Time for a Gedankenfeckabaht or some such thing: imagien you write a computer programme that simulates a day-night cycle of temperatures and plots a graph on the screen. Add a year-long seasonal "wave" and a four-day-long "low pressure system passing through" wave and a 3-year El Niño / La Nina cycle and a 7-year solar cycle. You'll get a wave pattern that repeats every 21 years, right? Add a 10-year cycle and you'll get one that repeats every 210 years. Sure. Whatever. Add some randomisation. Add random chance of a high-pressure system taking over for a few days. Add random fluctuations in the strength of the EN/LN oscillation. Add tracking of records. Track the hottest, coldest, wettest, driest, windiest, stillest, sunniest and dullest day, week, month, quarter, spring, summer, autumn, winter and year. Mark on the timeline when a record is set. What'd you expect? Lots of records in the first year, to be sure, because the first day is the hottest and coldest day on record, the first summer the hottest and mildest, the first winter the coldest and mildest, but after 42 years you wouldn't expect to see many records being set, after 63 you'd expect fewer and so on. We're seeing more and more records being set. RAM leak, if it's a computer simulation, or Something Going Awry if it's the only real world we've got.

Bear in mind that a river valley coloured in blue on that map isn't just "this part will be wet." It's "this part will be SALTY and wet." You can't keep growing the same food on a field that's got salt water seeping up into it.

Back to those record weather events. They're expected to get more frequent and more severe. That's more and more places looking less and less habitable. That means more and more people on the move, competing for places in more habitable areas. Can't blame them. Your child starves, your child drowns, your child is sold into slavery or you punch that shouty guy over there in the face and your child has a Western European child's future? Yeah, when it comes to it people try to survive, try to give their children a chance to survive and prosper and try, thanks to millennia of evolution, to have healthy great-grandchildren whether or not they'll ever see them. Are the people fleeing from drought, flood, salinity, desertification, conflict and so on going to be welcomed? By some, yes. Humans may not be wolves, but we can be friendly, sometimes.

Sometimes. Sometimes we're downright hostile to the perceived "other," usually when resources are scarce and the economy's under strain. When, in short, people perceive that there isn't enough for all the children to prosper and want to make sure that their own tribe's children do.

Whether it'll kill 1 billion people, well, how many people did the 2003 invasion of Iraq kill? Do you count the deaths from the civil war that followed? Do you count the victims of the London and Madrid bombings? Do you blame the situation in Syria on the invasion of Iraq? Do you blame the invasion for 8000 people drowning in the Med, or for some fraction of those?

... apparently can breed here, in some cases. There's not much difference, climatically, between southern England now and southern France when that survey was done. What if the climate of southern England gets more like the climate of Turkey ...

... and drug resistance means they need a new colour to indicate "unable to control malaria" and our wonderful Tories succeed in replacing universal healthcare with US-style private healthcare available only to the upper three quartiles of the income range and those anti-malarials get very expensive?

Jesus H. Stones. No one is going to look at all fifty-seven - by my count - of those links you posted.

There's a certain amount of freedom involved in cycling: you're self-propelled and decide exactly where to go. If you see something that catches your eye to the left, you can veer off there, which isn't so easy in a car, and you can't cover as much ground walking.

2. Methane clathrate gun hypothesis, causing the death of all life on earth except extremophiles/methane breathers.

Yes, these possibilities are far in the future (probably), but feedback loops are easiest to stop before they grow exponentially. If we start noticing the wide-scale effect of any of these situations, its already too late to do anything about it.

"Does this smell like chloroform to you?""Google tells me you are not unique. You are, however, wrong."nɒʜƚɒɿ_nɒɿɘ

Sableagle wrote:Still, what else is there to do when asked about it but try to answer or say "fuck nature" and drive a 4x4 through a nature reserve?

How about begin a conversation and suggest search terms? If I came up to you in-person and asked you this question, would you launch into an hour-long online search followed by 15 minutes of you lecturing me without giving me the opportunity to respond?

No, they won't, because we have no idea which ones might have some relevant value. If you're unable to synthesize information into a point that only takes a couple sentences to get across, you aren't helping or informing anyone.

There's a certain amount of freedom involved in cycling: you're self-propelled and decide exactly where to go. If you see something that catches your eye to the left, you can veer off there, which isn't so easy in a car, and you can't cover as much ground walking.

(Excepting the expected raw-link-abbreviation behaviour by the forum, but hover-over will still tell you.)

Another treatment: https://www.quora.com/What-percentage-o ... -sea-level(Note the bit about the higher high tides being important, as lower altitudes above MSL are already currently 'inundated land' where few people live outside of stilted buildings, but immediately above high tide people have settled in ways that "no longer being above high tides" (or reasonably expected storm surges) is already problematic.

Obviously if you can move people elsewhere (the flooding inland of flooded-out internal migrants making the present day fears of flooding by immigrants almost inconsequential) without causing disruption, then it's not a problem. Good luck with that. Best to just deny that it'll happen, rather than think about what to do if it does become consistent reality, right..?

No, they won't, because we have no idea which ones might have some relevant value. If you're unable to synthesize information into a point that only takes a couple sentences to get across, you aren't helping or informing anyone.

And because this is the Science subforum, I can say that in red:

If I can't reasonably guess about the specific content of a linked page from other information in the post, then it's a bad link and you should feel bad for having included it.

Sableagle, you in particular have been warned about this, more than once. Do it again and I'll simply remove your posting rights entirely.

Unless stated otherwise, I do not care whether a statement, by itself, constitutes a persuasive political argument. I care whether it's true.---If this post has math that doesn't work for you, use TeX the World for Firefox or Chrome

The goto source for this is the ’workgroup 2' report of the IPCC. The IPCC has three workgroups, 1 for the physical climate science itself, 2 for consequences, 3 for prevention and mitigation. The workgroup 2 report( which comes out every few years) is close as you'll get to a scientific consensus on the consequences of climate change.

p1t1o wrote:One camp says many species will become extinct due to rapid changes in the environment and habitats.Another camp says "SO what? Extinctions occur all the time."

Yes, extinctions happen all the time. The problem is that the rate of change of extinctions can change dramatically. The background rate of extinctions is estimated to be of order ~1 species/year. The current rate of extinction is ~1000 species/year (See here). So the problem is not that "species go extinct all the time", the problem is "the number of species that will go extinct THIS YEAR" is equal to the number of species that go extinct in a typical millennium". We're at risk of losing entire classes of species--the bulk of amphibians, in particular, could be wiped out by the 2200.

I think the 2007-2008 food crisis is instructive here. During 2007-2008, a variety of factors including increasing oil prices, droughts, population growth, price speculation, etc. caused food prices to jump between 100-200% in a one year period. This resulted in destabilization of dozens of impoverished countries and put millions at starvation risk. Although prices fell briefly following the 2008 recession, they've never fallen back to 2006 levels, and are actually above the peak of the crisis level at present. And there wasn't any factors involved that were even particularly severe. The global food supply is extremely, dangerously sensitive. Even if it is true that increased CO2 levels will create more arable land for us to use, that doesn't do any good if it destroys the arable land that we currently have, because the transition period is going to be extremely destabilizing. If a fairly minor shock to the food supply can send prices up 100% or more, what happens if it's a really major one?

One camp says global population redistribution due to changes in climate will cause havoc.Another camp says more of the planet will become habitable if the temperature rises.

Pretty much the same as above. The fact that people might be able to live on Antarctica sometime in the next hundred years is of little gain to us if it means nobody can live in China over the same period. There's no easy way to move a billion-plus people out of the high risk areas into the newly habitable ones.

Generally, I think it's important to think about the scales at play here. It would be very difficult for us to do so much damage to the biosphere that the Earth could no longer support life. It is not so very difficult for us to do so much damage to the biosphere that the Earth can no longer support human life, or the lives of the species that we depend on. It is probably fairly easy for us to do so much damage to the biosphere that the Earth can no longer support the quality of life that a 21st Century person living in the Western world might expect. What is scary about climate change is not that the climate is changing (it always does), but that the rate of change is extraordinarily fast. If the rate of change exceeds our ability, or the biosphere's ability, to keep pace, then we could be faced with catastrophic consequences.

Also, the human population was never as large as it is now. A change that would have driven a few nomadic tribes to migrate to a new place will be absolutely disastrous to today's densely inhabited countries and their equally densely inhabited neighbours.

What happens when only a few million people endeavour to migrate from the middle east to europe can be seen live right now.

I'm a bit late to the party I know, but I thought I'd give some observations on why there is still so much disagreement about climate change, when the science is getting more and more certain:

A: Climate is not weather. It's hard to predict weather more than a week or so in advance, due to nonlinearities etc. Climate models are much more predictable. Up until about 2010 there wasn't really enough data which meant substantial uncertainties in predictions, as there is for long range weather forecasts (although not really for the same reasons). This led to 2 responses.

1: One camp said that since we couldn't predict climate very well then what was the point of worrying about climate change.2: The other camp said that the uncertainty meant that we could well be approaching a tipping point and should take action to substantially cut CO2 right away.

Around 2010 though there was enough data to limit the uncertainty in the models, which showed that it was highly likely that the temperature would continue to increase slowly. The conclusion was that if we can cut CO2 output by 60% by 2050 with further cuts after that then we would probably be OK.

B:Lukewarmers.Climate change deniers seem to make claims in the hope that the reader won't know about the refutations of their claim that already exist. For those who disagree about whether the effects will be as bad as claimed (the so called 'Lukewarmers') the situation is less clear cut. People such as Bjorn Lomborg and Matt Ridley will enter into more protracted arguments and find the weak points in their opponents' position. Part of the problem is that their opponents are used to dealing with deniers, and lukewarmers need a different approach.

Overall I would say that the biggest problem is human inertia, firstly because it means people are still repeating the same arguments from 20 years ago and secondly because it means that even a gradual reduction in CO2 output is likely to be thwarted by our tendency to keep on burning fuels as we have done in the past.

A quarter of England’s rivers are at risk of running dry ... The driest October-to-March period for 20 years this year was followed by an extremely dry April and below average rainfall in May, and has left much of Britain with low river and groundwater levels and facing the possibility of drought. England hosts most of the world’s chalk streams but these are particularly vulnerable and half are now at risk of drying up, according to WWF.The government’s official advisers, the Committee on Climate Change (CCC), warned in 2016 that water shortages were one of the most serious impacts of global warming in Britain, with even modest temperature rises leading to “severe” water shortages in England.

[url=http://www.metoffice.gov.uk/news/releases/2017/high-risk-of-unprecedented-rainfall]New innovative research has found that for England and Wales there is a 1 in 3 chance of a new monthly rainfall record in at least one region each winter (Oct-Mar).

“The new Met Office supercomputer was used to simulate thousands of possible winters, some of them much more extreme than we’ve yet witnessed. This gave many more extreme events than have happened in the real world, helping us work out how severe things could get.”

The research has demonstrated that, even with the current climate, it is likely that there will be one or more monthly regional rainfall record events, in the coming decade.

It's not clear whether they mean regional rainfall records for 1750-2017 are likely to be broken in several regions over the next decade or that some regions are likely to break those records and then break the new records and even break those records over the next decade. Either way, it's not a very encouraging thought.

Drought is bad. Flooding is bad.Getting your country hit by both in different places at the same time is worse.One region of the country getting hit by both of them in sequence is even worse than that.

Extreme cold, meanwhile, is also linked to climate change and applies a squeeze from the other side, narrowing the "Goldilocks zone" of our own planet while more of it disappears under salt water. That's going to put some stress on food production and distribution, and our usual response to that is what? Cutting down more ancient forest? Feedback loop detected. I wonder how badly a single really harsh winter affects food production over the next several years. There must be thresholds where it starts killing off orchards or delays planting beyond a critical date or rots all the tubers or something.

Catastrophic changes in global weather patterns could be on the horizon as scientists confirm the warming Atlantic current has reached a “new record low”.

The Gulf Stream current, which has not been running at peak strength for centuries, is now at its weakest point in the past 1,600 years.

Climate change resulting from rising levels of carbon dioxide in the atmosphere is a likely cause of this phenomenon.

The Atlantic meridional overturning circulation (Amoc), the system of currents that transports warm water from the tropics via the Gulf Stream to the North Atlantic, plays a major role in regulating the world’s climate.

Two international teams of scientists have undertaken extensive analyses of sea surface temperature data and underwater sediments. Both studies were published in the journal Nature.

The early science on this one I saw years ago predicted that it would happen unless we Did Something about climate change, and the big question they had was how soon, because if we had 50 years of global warming before it collapsed we'd get the worst winter of the 19th Century every 7 years but if we only had 25 the port of Dover would be closed due to sea ice.

“If the more extreme case happened with the shutdown of the circulation then yes it is the case that Britain could cool – and it could cool by quite a lot, maybe 5 degrees Celsius,” said Dr Thornalley.

One such estimate suggested a 5 per cent chance that Amoc could collapse by the year 2100. While this is fairly low, Dr Thornalley pointed out this is a matter of perspective.

As the Amoc slows down, winter storms in the UK will become more prevalent, as will summer heatwaves across Europe. There will also be a rise in sea levels on the East Coast of the US, and an overall increase in sea temperatures will impact marine life in the Atlantic.

This tiny map: gives some context for 5°C cooler: from Porto to Inverness, from Inverness to Oslo and from Oslo to Tromsø.

In summer 2010, the largest landslide in Canadian history occurred on the southern part of the volcano.

“The glacier base of the slope retreated and during the hottest part of the summer, the slope catastrophically failed – the whole mountain started to move at a very high velocity,” said Mr Roberti.

This was followed in 2016 by the formation of ice caves in the glacier as hot volcanic gases seeped out of the volcano.

“This is the first time this has happened there – so the equilibrium of the mountain is changing,” said Mr Roberti.

To understand these events, the scientists used numerical modelling of the volcano to examine the link between melting ice on the glacier and changes to the magma “plumbing system” inside it.

They found that landslides had the potential to destabilise the magma chamber and trigger an eruption – a phenomenon that can be linked directly to a warmer climate.

“This new research nicely demonstrates that if you change the load on a volcanic mountain – for example by removing some ice – the likelihood of a mechanical collapse and possible ensuing eruption will be slightly increased,” said Professor David Rothery, a geoscientist at The Open University who was not involved in the research.

“Eruptions are triggered by a complex array of factors. I suspect that many eruptions caused by glacial melting might happen eventually anyway, given enough time – but this research shows that warming could increase the chances of those eruptions happening sooner rather than later.”

I'm not a denier in any way (I trust scientists to know what they're talking about) but the consequences that I've read about, including in this thread, still don't seem to warrant the kind of panic that some people seem to be having. If we shift to having a cozy Greenland and arable Canada while New York gets submerged and Kansas becomes a desert, but that takes a century or two to happen, that sounds like something that humans are more than able to adapt to. The city I live in basically didn't exist a century ago, and the country I live in is just slightly over two centuries old.

As sea levels and deserts encroach on currently inhabited places, those people on the border of the change will face gradual pressure to move, and places that are unlivable now will be opening up and people will be moving to them. It's not like we have to suddenly relocate everyone in New York to Greenland right now or they'll all die. It's still a bad thing, sure, that will cost a lot of money and inconvenience in the long term and no doubt plenty of hardship and even death along the way, but not a world-is-ending-everybody-panic kind of bad thing. The climate-unrelated housing crisis in California (for example) seems to be a more urgent threat to displacing millions of people than a century-long shift in what places have what climate (e.g. something like 75% of residents are statistically unable to afford housing, and something like 33% of them are thinking of leaving because of that; that's 10-20 million people we're talking about displacing right now, not over a century).

It's not just the fact that people will be displaced, it's that it's going to create an imbalance in the ecosystem that will take centuries to correct. In the ocean, especially, climate change is already causing extinctions, and once parts of the food supply start to go extinct it can cause more and more extinctions. That itself will affect the food supply of a very large number of people when we aren't even feeding everyone today.

It adds a huge amount of uncertainty, and so far humanity has shown itself unwilling and unable to plan for the future (which, I'd argue our economy is structured to maximize uncertainty as it stands), which means this will likely trigger repeated crises throughout the future including war and famine because we will simply be unable to adapt to the changes (which some are saying climate change has already contributed to the wars in the middle east), and it will mean many many economic meltdowns, not to mention that we will have to devote a lot more resources to resolving crises, which will make it harder to solve the other crises that will happen in the future regardless.

Yeah it's only hundreds of millions of people's lives destroyed, not billions. Why is everyone so concerned?

Unless stated otherwise, I do not care whether a statement, by itself, constitutes a persuasive political argument. I care whether it's true.---If this post has math that doesn't work for you, use TeX the World for Firefox or Chrome

[...]The city I live in basically didn't exist a century ago, and the country I live in is just slightly over two centuries old.

As sea levels and deserts encroach on currently inhabited places, those people on the border of the change will face gradual pressure to move, and places that are unlivable now will be opening up and people will be moving to them. [...]

Your example is not that comforting, IMO. The large European migration wave was based on total (and brutal) control of the areas to be settled, and it was everywhere horrible for the original population.

And it moved, over the centuries, only something like 10 to 20% of the European population. Your hypothetical climate change resettlement would have to be much more intense, and it would be worldwide. In practice, it would easily become Generalplan Nord or Manifest Destiny: Canada Edition, and everyone else praying that no one has their home targeted for Gradual Pressure.

When UN climate negotiators meet for summit talks this month, there will be a new figure on the table: 3C.

Until now, global efforts such as the Paris climate agreement have tried to limit global warming to 2C above pre-industrial levels. However, with latest projections pointing to an increase of 3.2C by 2100, these goals seem to be slipping out of reach.

Scientists at the non-profit organisation Climate Central estimate that 275 million people worldwide live in areas that will eventually be flooded at 3C of global warming.

As a result of global sea-level rise, storm surges and other factors, economists project that coastal flooding could put almost $1tn of Osaka’s assets at risk by the 2070s, according to the Union of Concerned Scientists. “In the past our response was focused on reducing the causes of global warming, but given that climate change is inevitable, according to the Intergovernmental Panel on Climate Change (IPCC), we are now discussing how to respond to the natural disasters that will follow,” Nakaaki said.[/quote]

Probably the best thread for it: I remember reading this collection of handwritten letters from climate scientists expressing their frustrations, fears, etc. Does anyone know what I'm talking about?

There's a certain amount of freedom involved in cycling: you're self-propelled and decide exactly where to go. If you see something that catches your eye to the left, you can veer off there, which isn't so easy in a car, and you can't cover as much ground walking.

There's a certain amount of freedom involved in cycling: you're self-propelled and decide exactly where to go. If you see something that catches your eye to the left, you can veer off there, which isn't so easy in a car, and you can't cover as much ground walking.

[url=https://www.youtube.com/watch?v=ZlojvcmgfQA]So I'm getting probabilities on all these slides here, and those probabilities are 30-year probabilities of a $100bn weather disaster, in increasing cost.

1. The climate becomes warmer, the glacier melts and the sea level will rise, causing the loss of ecosystems, such as the coastal wetlands, mangroves and coral reefs, the coastal erosion, the invasion of the coastal groundwater and the salinization of the coastal land, resulting in the natural environmental imbalance of the coastal, estuarine and Gulf, and the ecological environment of the coastal zone. Bring disaster.2. The area of water area is increased. Water evaporation is also more frequent, and the flood season is becoming more frequent as the rainy season lengthen. The life span of reservoir dams is shortened due to the increase of flood opportunities and the severity and severity of storms.3. The rising temperature may melt the ice and snow in Antarctic Peninsula and the Arctic Ocean. The polar bears and the walrus are going to be extinct.4. Many small islands will be lost; infectious diseases such as malaria will be infected.5. Because of the effect of thermal inertia, the existing greenhouse gases will continue to affect our lives. "6. Higher temperature will affect people's fertility. Sperm activity decreases with increasing temperature. .7. The speed of the satellite will also accelerate, and the mountains will be higher.

The main cause of sea level rise currently is thermal expansion from global warming. But I imagine at some point, sea level rise (flux) due to melting and calving of glaciers and ice sheets will be greater. Does anyone know when that would happen?

Eebster the Great wrote:The main cause of sea level rise currently is thermal expansion from global warming. But I imagine at some point, sea level rise (flux) due to melting and calving of glaciers and ice sheets will be greater. Does anyone know when that would happen?

As the ocean warms, the density decreases and thus even at constant mass the volume of the ocean increases. This thermal expansion (or steric sea level rise) occurs at all ocean temperatures and is one of the major contributors to sea level changes during the 20th and 21st centuries. Water at higher temperature or under greater pressure (i.e., at greater depth) expands more for a given heat input, so the global average expansion is affected by the distribution of heat within the ocean. Salinity changes within the ocean also have a significant impact on the local density and thus local sea level, but have little effect on global average sea level change.

The rate of climate change depends strongly on the rate at which heat is removed from the ocean surface layers into the ocean interior; if heat is taken up more readily, climate change is retarded but sea level rises more rapidly. Climate change simulation requires a model which represents the sequestration of heat in the ocean and the evolution of temperature as a function of depth.

The large heat capacity of the ocean means that there will be considerable delay before the full effects of surface warming are felt throughout the depth of the ocean. As a result, the ocean will not be in equilibrium and global average sea level will continue to rise for centuries after atmospheric greenhouse gas concentrations have stabilised.

In summary, while the evidence is still incomplete, there are widespread indications of thermal expansion, particularly in the sub-tropical gyres, of the order 1 mm/yr (Table 11.1).

A variety of ocean models have been employed for estimates of ocean thermal expansion. The simplest and most frequently quoted is the one-dimensional (depth) upwelling-diffusion (UD) model (Hoffert et al., 1980; Wigley and Raper, 1987, 1992, 1993; Schlesinger and Jiang, 1990; Raper et al., 1996), which represents the variation of temperature with depth. Kattenberg et al. (1996) demonstated that results from the GFDL AOGCM could be reproduced by the UD model of Raper et al. (1996). Using this model, the best estimate of thermal expansion from 1880 to 1990 was 43 mm (with a range of 31 to 57 mm) (Warrick et al., 1996). Raper and Cubasch (1996) and Raper et al. (2001) discuss ways in which the UD model requires modification to reproduce the results of other AOGCMs. The latter work shows that a UD model of the type used in the SAR may be inadequate to represent heat uptake into the deep ocean on the time-scale of centuries. De Wolde et al. (1995, 1997) developed a two dimensional (latitude-depth, zonally averaged) ocean model, with similar physics to the UD model. Their best estimate of ocean thermal expansion in a model forced by observed sea surface temperatures over the last 100 years was 35 mm (with a range of 22 to 51 mm). Church et al. (1991) developed a subduction model in which heat is carried into the ocean interior through an advective process, which they argued better represented the oceans with movement of water along density surfaces and little vertical mixing. Jackett et al. (2000) developed this model further and tuned it by comparison with an AOGCM, obtaining an estimate of 50 mm of thermal expansion over the last 100 years.

A number of model simulations of the 20th century (Table 9.1) have recently been completed using realistic greenhouse gas and aerosol forcings. Results for global average thermal expansion over periods during the 20th century are given in Figure 11.1 and Table 11.2. They suggest that over the last hundred years the average rate of sea level rise due to thermal expansion was of the order of 0.3 to 0.7 mm/yr, a range which encompasses the simple model estimates, rising to 0.6 to 1.1 mm/yr in recent decades, similar to the observational estimates (Section 11.2.1.1).

Estimates of the historical global glacier contribution to sea level rise are shown in Table 11.4. Dyurgerov and Meier (1997a) obtained their estimate by dividing a large sample of measured glaciers into seven major regions and finding the mass balance for each region, including the glaciers around the ice sheets. Their area-weighted average for 1961 to 1990 was equivalent to 0.25 ± 0.10 mm/yr of sea level rise. Cogley and Adams (1998) estimated a lower rate for 1961 to 1990. However, their results may be not be representative of the global average because they do not make a correction for the regional biases in the sample of well investigated glaciers (Oerlemans, 1999).

Both the observations of mass balance and the estimates based on temperature changes (Table 11.4) indicate a reduction of mass of glaciers and ice caps in the recent past, giving a contribution to global-average sea level of 0.2 to 0.4 mm/yr over the last hundred years.

[url=http://www.ipcc.ch/ipccreports/tar/wg1/416.htm]Together, the present Greenland and Antarctic ice sheets contain enough water to raise sea level by almost 70 m (Table 11.3), so that only a small fractional change in their volume would have a significant effect. The average annual solid precipitation falling onto the ice sheets is equivalent to 6.5 mm of sea level, this input being approximately balanced by loss from melting and iceberg calving.[url]

For Greenland (Table 11.5), runoff is an important term but net ablation has only been measured directly at a few locations and therefore has to be calculated from models, which have considerable sensitivity to the surface elevation data set and the parameters of the melt and refreezing methods used (Reeh and Starzer, 1996; Van de Wal, 1996; Van de Wal and Ekholm, 1996; Janssens and Huybrechts, 2000). Summing best estimates of the various mass balance components for Greenland gives a balance of -8.5 ± 10.2% of the input, or +0.12 ± 0.15 mm/yr of global sea level change, not significantly different from zero.

For Antarctica (Table 11.6), the ice discharge dominates the uncertainty in the mass balance of the grounded ice sheet, because of the difficulty of determining the position and thickness of ice at the grounding line and the need for assumptions about the vertical distribution of velocity. The figure of Budd and Smith (1985) of 1,620x1012 kg/yr is the only available estimate. Comparing this with an average value of recent accumulation estimates for the grounded ice sheet would suggest a positive mass balance of around +10% of the total input, equivalent to -0.5 mm/yr of sea level. Alternatively, the flux across the grounding line can be obtained by assuming the ice shelves to be in balance and using estimates of the calving rate (production of icebergs), the rate of melting on the (submerged) underside of the ice shelves, and accumulation on the ice shelves. This results in a flux of 2,209 ± 391x1012 kg/yr across the grounding line and a mass balance for the grounded ice equivalent to +1.04 ± 1.06 mm/yr of sea level (Table 11.6). However, the ice shelves may not be in balance, so that the error estimate probably understates the true uncertainty.

In a recent update, Krabill et al. (2000) find the total ice sheet balance to be -46x1012 kg/yr or 0.13 mm/yr of sea level rise between 1993 and 1999, but could not provide an error bar. Incidentally, this value is very close to the century time-scale imbalance derived from the mass budget studies (Table 11.5), although the time periods are different and the laser altimetry results do not allow us to distinguish between accumulation, ablation, and discharge.

That "not significantly different from zero" is because the error bar stretches beyond zero. I'd expect lobbyists to jump on that phrase and abuse the hell out of it. It's hard to come up with a comparison. Maybe a carnival game? You pay $10 to play, and you get back $10.30, $10.10, $9.90, $9.70, $9.50, $9.40, $9.30, $9.20, $9.10, $9.05, $9.00, $8.95, $8.90, $8.85, $8.80, $8.75, $8.70, $8.65, $8.60, $8.55, $8.50, $8.40, $8.30, $8.20, $8.10, $7.90, $7.70, $7.50 or $7.30, so you're not sure you're going to lose money by playing this game and your return on investment is "not significantly different from zero" so go right ahead.

White Sun wrote:6. Higher temperature will affect people's fertility. Sperm activity decreases with increasing temperature. .7. The speed of the satellite will also accelerate, and the mountains will be higher.

Eebster the Great wrote:The main cause of sea level rise currently is thermal expansion from global warming. But I imagine at some point, sea level rise (flux) due to melting and calving of glaciers and ice sheets will be greater. Does anyone know when that would happen?

As the ocean warms, the density decreases and thus even at constant mass the volume of the ocean increases. This thermal expansion (or steric sea level rise) occurs at all ocean temperatures and is one of the major contributors to sea level changes during the 20th and 21st centuries. Water at higher temperature or under greater pressure (i.e., at greater depth) expands more for a given heat input, so the global average expansion is affected by the distribution of heat within the ocean. Salinity changes within the ocean also have a significant impact on the local density and thus local sea level, but have little effect on global average sea level change.

The rate of climate change depends strongly on the rate at which heat is removed from the ocean surface layers into the ocean interior; if heat is taken up more readily, climate change is retarded but sea level rises more rapidly. Climate change simulation requires a model which represents the sequestration of heat in the ocean and the evolution of temperature as a function of depth.

The large heat capacity of the ocean means that there will be considerable delay before the full effects of surface warming are felt throughout the depth of the ocean. As a result, the ocean will not be in equilibrium and global average sea level will continue to rise for centuries after atmospheric greenhouse gas concentrations have stabilised.

In summary, while the evidence is still incomplete, there are widespread indications of thermal expansion, particularly in the sub-tropical gyres, of the order 1 mm/yr (Table 11.1).

A variety of ocean models have been employed for estimates of ocean thermal expansion. The simplest and most frequently quoted is the one-dimensional (depth) upwelling-diffusion (UD) model (Hoffert et al., 1980; Wigley and Raper, 1987, 1992, 1993; Schlesinger and Jiang, 1990; Raper et al., 1996), which represents the variation of temperature with depth. Kattenberg et al. (1996) demonstated that results from the GFDL AOGCM could be reproduced by the UD model of Raper et al. (1996). Using this model, the best estimate of thermal expansion from 1880 to 1990 was 43 mm (with a range of 31 to 57 mm) (Warrick et al., 1996). Raper and Cubasch (1996) and Raper et al. (2001) discuss ways in which the UD model requires modification to reproduce the results of other AOGCMs. The latter work shows that a UD model of the type used in the SAR may be inadequate to represent heat uptake into the deep ocean on the time-scale of centuries. De Wolde et al. (1995, 1997) developed a two dimensional (latitude-depth, zonally averaged) ocean model, with similar physics to the UD model. Their best estimate of ocean thermal expansion in a model forced by observed sea surface temperatures over the last 100 years was 35 mm (with a range of 22 to 51 mm). Church et al. (1991) developed a subduction model in which heat is carried into the ocean interior through an advective process, which they argued better represented the oceans with movement of water along density surfaces and little vertical mixing. Jackett et al. (2000) developed this model further and tuned it by comparison with an AOGCM, obtaining an estimate of 50 mm of thermal expansion over the last 100 years.

A number of model simulations of the 20th century (Table 9.1) have recently been completed using realistic greenhouse gas and aerosol forcings. Results for global average thermal expansion over periods during the 20th century are given in Figure 11.1 and Table 11.2. They suggest that over the last hundred years the average rate of sea level rise due to thermal expansion was of the order of 0.3 to 0.7 mm/yr, a range which encompasses the simple model estimates, rising to 0.6 to 1.1 mm/yr in recent decades, similar to the observational estimates (Section 11.2.1.1).

Estimates of the historical global glacier contribution to sea level rise are shown in Table 11.4. Dyurgerov and Meier (1997a) obtained their estimate by dividing a large sample of measured glaciers into seven major regions and finding the mass balance for each region, including the glaciers around the ice sheets. Their area-weighted average for 1961 to 1990 was equivalent to 0.25 ± 0.10 mm/yr of sea level rise. Cogley and Adams (1998) estimated a lower rate for 1961 to 1990. However, their results may be not be representative of the global average because they do not make a correction for the regional biases in the sample of well investigated glaciers (Oerlemans, 1999).

Both the observations of mass balance and the estimates based on temperature changes (Table 11.4) indicate a reduction of mass of glaciers and ice caps in the recent past, giving a contribution to global-average sea level of 0.2 to 0.4 mm/yr over the last hundred years.

[url=http://www.ipcc.ch/ipccreports/tar/wg1/416.htm]Together, the present Greenland and Antarctic ice sheets contain enough water to raise sea level by almost 70 m (Table 11.3), so that only a small fractional change in their volume would have a significant effect. The average annual solid precipitation falling onto the ice sheets is equivalent to 6.5 mm of sea level, this input being approximately balanced by loss from melting and iceberg calving.[url]

For Greenland (Table 11.5), runoff is an important term but net ablation has only been measured directly at a few locations and therefore has to be calculated from models, which have considerable sensitivity to the surface elevation data set and the parameters of the melt and refreezing methods used (Reeh and Starzer, 1996; Van de Wal, 1996; Van de Wal and Ekholm, 1996; Janssens and Huybrechts, 2000). Summing best estimates of the various mass balance components for Greenland gives a balance of -8.5 ± 10.2% of the input, or +0.12 ± 0.15 mm/yr of global sea level change, not significantly different from zero.

For Antarctica (Table 11.6), the ice discharge dominates the uncertainty in the mass balance of the grounded ice sheet, because of the difficulty of determining the position and thickness of ice at the grounding line and the need for assumptions about the vertical distribution of velocity. The figure of Budd and Smith (1985) of 1,620x1012 kg/yr is the only available estimate. Comparing this with an average value of recent accumulation estimates for the grounded ice sheet would suggest a positive mass balance of around +10% of the total input, equivalent to -0.5 mm/yr of sea level. Alternatively, the flux across the grounding line can be obtained by assuming the ice shelves to be in balance and using estimates of the calving rate (production of icebergs), the rate of melting on the (submerged) underside of the ice shelves, and accumulation on the ice shelves. This results in a flux of 2,209 ± 391x1012 kg/yr across the grounding line and a mass balance for the grounded ice equivalent to +1.04 ± 1.06 mm/yr of sea level (Table 11.6). However, the ice shelves may not be in balance, so that the error estimate probably understates the true uncertainty.

In a recent update, Krabill et al. (2000) find the total ice sheet balance to be -46x1012 kg/yr or 0.13 mm/yr of sea level rise between 1993 and 1999, but could not provide an error bar. Incidentally, this value is very close to the century time-scale imbalance derived from the mass budget studies (Table 11.5), although the time periods are different and the laser altimetry results do not allow us to distinguish between accumulation, ablation, and discharge.

That "not significantly different from zero" is because the error bar stretches beyond zero. I'd expect lobbyists to jump on that phrase and abuse the hell out of it. It's hard to come up with a comparison. Maybe a carnival game? You pay $10 to play, and you get back $10.30, $10.10, $9.90, $9.70, $9.50, $9.40, $9.30, $9.20, $9.10, $9.05, $9.00, $8.95, $8.90, $8.85, $8.80, $8.75, $8.70, $8.65, $8.60, $8.55, $8.50, $8.40, $8.30, $8.20, $8.10, $7.90, $7.70, $7.50 or $7.30, so you're not sure you're going to lose money by playing this game and your return on investment is "not significantly different from zero" so go right ahead.

Cool, thanks. But the data is quite old, and unfortunately it doesn't directly answer my question though. It seems like both ice loss and thermal expansion will accelerate with increasing temperature, and ice loss should eventually dominate, but I already knew that. It does not suggest when ice loss should dominate expansion.

As of a few weeks ago, babies born in the UK are likely to live long enough to see all the effects of climate change that'll happen "by 2100."

Not so far off, eh?

I read that bit about the satellite speed and mountain height, I drank beer, I read it again, I went to bed, I slept, I came back and I read it again and it still makes no sense to me at all. Is this one of those chemtrail things?